There’s a lot of information available on how to make water safe to drink. That’s a good thing because water is one of the most important parts of our survival and comfort. My goal in this article is to organize and describe some of these methods in a way that is interesting and easy to read. I have included a few internet links to more detailed step-by-step descriptions and how-to videos created by others.
Although important, I’m won’t go into all the diseases and problems that can be caused by ingesting contaminated water. Just know that there is some bad stuff out there that can make a survival situation worse than if you didn’t drink the water at all. Additionally, I understand there are differences between the terms PURIFICATION, DISINFECTION, and FILTERED. I don’t want to get into all those details in this article. When making water safe you want to choose the most effective method with the materials available.
In all methods listed below an attempt should be made to pre-filter large contaminates before beginning the disinfection process.
I have listed some of the methods below in two different ways; a brief description and then a detailed description.
Brief Descriptions of methods:
Boiling: Bring water to a rolling boil for at least one minute.
Distillation: Converting water into a vapor and then back into a liquid via direct or solar heat.
Commercial Filter: A product designed and manufactured specifically for purifying water. These usually contain some type of charcoal or ceramic filter.
Chemical: Using water purifications tablets, chlorine (bleach) and iodine.
Solar Disinfection (SODIS): Exposing water filled transparent bottles to the sun for an extended period of time.
Improvised Filter: Using multiple layers and combinations of sand, rocks, pebbles, grass and cloth to create a filter similar to how the ground naturally filters water.
Detailed Descriptions of Methods:
Boiling: Boiling water is probably the most effective and reliable method of disinfecting water. To make water safe to drink by boiling the water needs to be at a rolling boil for at least one minute. Some sources may mention five or more minutes as the minimum but the extra time doesn’t provide any extra benefit and uses up more fuel. An exception to the time for the boiling would be in high elevations where three minutes is recommended.
Ensure the container has not been previously used to store dangerous substances. Metal containers are ideal for boiling water but other containers such as clay and plastic can be used as well.
A plastic container can also be used for boiling water. Place the full container as close to a heat source as possible without coming into direct contact. Keep it there until you see the water boiling for one minute. Here’s a video from the YouTube channel Wilderness Outfitters demonstrating this method: Boiling In Plastic Bottle [JWR Adds: If you have a thermometer (ideally a floating dairy thermometer, the oft-repeated “full boil” or rolling boil” is not required to disinfect clear (filtered) water. The magic number that needs to be touched for Pasteurizing is 65º C (149º F). But if you don’t have a thermometer, then bring the water briefly to just short of a boil (where the water visibly starts to churn), just to be safe.
Distillation: This method is similar to how nature creates rain. Heat transforms water into a vapor. The vapor will condensate when it comes into contact with a solid surface or enough of it collects together until it’s too heavy to be suspended in the air. There are several methods of making water safe via distillation. I will discuss solar distillation here.
Many survival manuals discuss creating a “Solar Still” to procure water from the moisture in soil or green vegetation but it can also be used on existing sources of water that are suspected of being contaminated.
The typical description of a solar still describes using a depression in the ground eighteen to twenty-four inches deep and about three feet wide. Green vegetation is placed inside along the sides. A collection container is placed on the ground in the middle and then the entire depression is covered with plastic sheeting. Cover the sides of the sheeting with soil or other heavy objects to hold it in place and create a seal. A small weight is placed on top of the covering directly above the collection container. This causes the covering to drop slightly in a cone shape so that the condensed water on the underside of the plastic sheeting will pool to the center and then drip into the collection container. You can run tubing from the collection container to the outside of the solar still and use as a straw so that you don’t have to disturb the cover when accessing the water. Here is a video posted on the YouTube channel Desert Survival demonstrating how to build a solar still: Solar Still
Potentially unsafe water can be placed into the solar still and it will be evaporated the same way that moisture from the green vegetation would be. You can pour the unsafe water directly into the depression or place in containers. It’s very important to not allow any of the contaminated water to come in contact with the collections container or the covering for the depression.
[JWR Adds a Proviso: As previously mentioned in SurvivalBlog, do not use distilled water as your only source of water for drinking and cooking for an extended period, since it lacks the essential trace minerals found in spring water, well water, or tap water.]
Commercial Filter: There are numerous types of products designed to mechanically purify water. The technology for these is constantly changing especially as more effective and efficient methods are developed for use in impoverished areas of the world.
They come in a variety of shapes and sizes. Most use a ceramic filter or activated charcoal to remove contaminates. There are pump-operated versions and some very simple straw types.
These types of filters can be expensive but their benefits would quickly outweigh the cost if they are ever needed in an emergency. Some major benefits are time and energy do not have to be expended in gathering fuel, starting a fire or waiting on chemicals to be effective etc.
I have provided a few links below of different types of filters and how they work. I’m not promoting any of these brands but simply directing you to them as examples of what a typical commercial filter looks like.
The following link has some examples of portable filters by one of the leading manufacturers of these devices: Katadyn Water Filters Here’s an explanation and demonstration of a pump filter on the YouTube channel, KatadynKP: Pump Filter
Here is an example of a filter straw: Aquamira Filter Straw This link has a great demonstration posted on the YouTube channel, ShelfReliance: Filter Straw Demonstration.
Chemical: There are a few different types of chemicals that will make water safe to drink. Some, like purification (iodine) tablets are made specifically for camping, hiking and emergency situations. Others, like household bleach and iodine tincture can be used safely if you know the proper ratios to use.
When using chemicals for disinfection in a container with a lid remember to loosen the lid about 5 minutes after adding the disinfectant and allow the water to come into contact with the threads and the inside of the lid. This will ensure no contaminates remain in those areas.
Water purification tablets are pretty straightforward. You drop the appropriate number of tablets into a container of water (usually about a quart) and wait about 30 minutes. The effective time will vary slightly depending on the clarity and temperature of the water. These types of tablets were standard issue in my infantry days in the army. They can be purchased just about anywhere camping gear is sold. An unopened container of the tablets can be good for a few years. Follow the directions on the label. Here’s a great demonstration posted on the YouTube channel, eHow: Water Purification Tablets
Household bleach (chlorine) is probably the most accessible method of disinfection for a typical family since it is such a common product in our homes. The bleach must not have additives such as scents, cleaners or be the “colorsafe” type. About 1/8th teaspoon can be added to a gallon of water. (16 drops if you have dropper.) After stirring let it sit for at least 30 minutes. Smell the solution to get a general idea if it was done correctly. There should be a slight chlorine smell similar to a swimming pool. If you do not smell the chlorine then you can repeat the procedure. If it still does not work the second time around then the bleach is probably not effective anymore. Bleach does not have a particular long shelf life especially after opening the container. “MrJmfitch” created a video of the bleach technique: Chlorine Bleach Disinfection
Iodine tincture solution is a handy item to have in your emergency kit because not only can it be used to disinfect water but it can be used in the treatment of wounds. Caution must be used for people with sensitivity to iodine.
It is recommended to use tincture with 2% iodine. Add about 5-8 drops of iodine to 1 liter of water and wait at least 30 minutes. Issues with the iodine taste of the water can be remedied by adding vitamin C after the 30 minute wait. Here is a step-by-step guide with pictures on the web site, Instructables. Iodine Purification
Solar Disinfection (SODIS): This method uses the suns UV radiation to disinfect contaminated water. Ideally a PET made container should be used. A typical plastic transparent water bottle would be an example of a PET made container. Here is more information on what a PET container is: PET Containers
Completely fill the bottle with the contaminated water and expose it to at least 6 hours of direct sunlight. If only partial sunlight is available then the time should be extend to several days.
An optional step I have read about is to agitate the container before it is completely full. This will oxygenate the water. Finish filling the container after oxygenating.
This link has detailed step-by-step instructions: SODIS Step-by-Step
Here’s a video demonstration of the SODIS method on the YouTube channel, wildernessinnovation: SODIS video
Improvised Filter: An improvised filter uses multiple layers of different materials to filter the water. It’s similar to how the earth naturally filters water. This method is certainly not the preferred method but is probably slightly better than drinking straight from the source.
Some type of container will be needed such as a bottle or a can but I’ve even seen this method demonstrated in a hole in the ground. Filter materials that can be used for this method include dirt, grass, charcoal, cloth and coffee filters. You will ideally need at least three different materials. The preferred ones would be grass, charcoal and dirt.
The top of the container will need to be removed so the materials can be layered into it. Smalls holes will are placed in the bottom of the container. They need to be the right size to allow the water to flow through them but not allow all of the filter materials to get through. You can start small and increase the size of the holes as needed.
The filter should have the coarsest materials on the top and bottom and as the layers get closer to the middle the finer materials are used. For example, at the bottom of the container would be grass, then on that would be dirt, then charcoal, dirt again and then another layer of grass at the top.
This link has an easy to follow step-by-step guide on the web site Practical Primitive: Improvised Water Filter
Here is a video demonstration from the YouTube channel eHow: Improvised Water Filter Video
Remember, you always want to use the most effective method of water purification with the materials on hand. You also need to factor in the time an energy that will be expended in the particular method you choose. In a worst case scenario there may be a chance that you have no method of ensuring water is safe to drink. If it comes down to dying of dehydration or possibly getting sick from drinking unsafe water, drink the water.